Method and apparatus for cleaning textiles

ABSTRACT

The invention relates to an apparatus for cleaning textiles by means of FCHC-free solvents on a benzine basis, comprising a cleaning machine, distillation section, recovery section and drier, and is characterized by a means for injecting protective gas into the drier.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for cleaning textiles in FCHC-freemanner by means of solvents on a benzine basis.

The invention also relates to the use of such a method.

2. Description of the Prior Art

Finally, the invention also relates to an apparatus for cleaningtextiles by means of FCHC-free solvents on a benzine basis comprising acleaning machine, distillation section, recovery section and drier.

Generally, in such a cleaning plant the drying takes place (aftertransferring the material from the cleaning machine) by means of hotair; the textile material in particular predried by spinning in a drumin the cleaning machine (for example down to 11% residual moisturecontent) is further dried and the cleaning agent is recovered from thesolvent-charged air by distillation and condensation.

However, particular safety precautions are necessary here because thesolvent on a benzine basis involves a considerable danger of explosion,at the least from the flashpoint of the solvent (71° C.) used upwards.Also, the operations under vacuum necessary because of this are verycomplicated. FCHCs are however allowed for only a short period and theuse of PER involves increasingly high demands on the apparatus quality,and consequently both the FCHC-operated and the PER-operated machinesmust be replaced or at least considerably modified. In addition, withall existing machines and the cleaning agents used therein a practically100% distillation was necessary due to the considerable contamination ofthe cleaning agent.

Also known is a method for dry cleaning with a hydrocarbon having a lowflashpoint (41° C.) and high vapour pressure (EP 90 119 398.7). Aso-called dry-to-dry cleaning machine is described, i.e. a machine inwhich both washing and drying is carried out. With this type of solvent,for safety, technical, humane-ecological and ecological reasonsreloading in the moist state is not compatible with European standards,in particular German standards. In this case hot air is forced inbetween the washing bath and the dry conduit and the evaporated solventcondensed for recovery. Before this solvent recovery step a partialvacuum is generated and an inert gas introduced. The inert gas ishowever introduced into the washing bath until the oxygen density of amixture containing a solvent assumes a value beneath a predeterminedlimit value. After the introduction of the inert gas into the washingbath (reduction of the oxygen density) washing, centrifuging and finallydrying are carried out.

SUMMARY OF THE INVENTION

To be more exact, the rendering inert therein takes place as follows:

a) Firstly by generating a partial vacuum, the aim being to achieve aresidual oxygen content of 5 vol. %. This means however that theoperations must be carried out with a gas-tight machine.

b) In addition, inert gas, presumably from a nitrogen tank, is injectedin to set the residual oxygen content to 5%. The method is technicallycomplicated and involves the aforementioned problems such as thetechnically involved vacuum method with gas-tight machine.

Compared therewith, the invention is based on the problem of providing amethod and an apparatus which operate not only PER-free and FCHC-freebut in addition reduce the expenditure considerably and with which thedrying operation can be carried out practically free of any danger evenwhen individual apparatus parts should fail in their function.

This is achieved in surprisingly simple manner with a method of the typeset forth at the beginning in that the drying is carried out under aprotective gas.

Preferably, the drying is carried out under nitrogen.

It is particularly expedient to carry out the drying with nitrogenobtained from the air, oxygen being filtered out of the air in a mannerknown per se.

Pressure bottles, separate connections, and the replacement of suchpressure bottles or tanks can be dispensed with if nitrogen obtained insitu is used for the drying.

Preferably, N2 is injected into the drier itself.

Preferably, the operation is carried out with an aroma-free solventknown per se and having a low evaporation value, in particularN-Undecane.

Expediently, the procedure is such that with a temperature of 55° C. inthe closed system drying is carried out in particular to 15° C. beneaththe theoretical flashpoint.

It is favourable to carry out the drying with an oxygen content of 6% inthe drying gas, i.e. with a value far below the explosion limit.

It is particularly advantageous to operate with nitrogen flushingwithout vacuum, and almost ambient pressure conditions can be employedduring the drying.

With the step according to the invention, FCHC(fluorochlorohydrocarbon)-operated apparatuses and PER-operatedapparatuses may be considered obsolete. After appropriate prespottingthe articles are cleaned in the cleaning machine, the latter being asprung machine which is provided with an upper gear-type motor drive. Ahigh centrifuging speed is possible and consequently 89% of the solventis extracted in spinning and only 11% later in the drier after thearticles have been transferred.

The transferring permits simultaneous operation of the drier andcleaning machine with the advantage that this doubles the capacity ofthe system compared with conventional dry-to-dry techniques. Thetransfer is made possible by the low evaporation value when N-Undecaneis used as cleaning agent. If two driers are employed in the system thecapacity of the apparatus may even be increased to three times thecharging value.

Furthermore, a distillation unit is provided, the capacity of which canbe limited to 70 liters per second due to the use of the N-Undecane,which can be handled without any problems. Hitherto, a distillation of100% was necessary but with the step of the invention 20% distillationsuffices. The distillation operates under vacuum.

Cartridge filters may be employed.

By connecting a refrigeration apparatus to the drier the cleaning agentcan be recovered practically completely and the solvent loss here is 1%.By employing this apparatus the theoretical danger of fire iseliminated. It is physically impossible for a flame to exist in thenitrogen air mixture created (oxygen content beneath 10% or beneath 6%).

The solvent used corresponds to the same risk class as light fuel oil.Contact water occurs only in small amounts.

Due to the inert gas (protective gas) production in the system anychange of bottles or supply tanks is eliminated; no follow-up costsarise for the protective gas.

Separate safety circuits are present in the system, firstly to keep thetemperature 15° C. beneath the flashpoint of the solvent (71° C.) andsecondly for monitoring the O2 concentration, trouble alarms being givenwith the O2 concentration rises above 6%. However, even at 10% there isno fear of any danger of explosion.

The apparatus for cleaning textiles by means of FCHC-free solvents on abenzine basis comprising a cleaning machine, distillation section,recovery section and drier is therefore distinguished by supplying ofprotective gas into the drier.

A metering conduit for N2 may be led from the reservoir of a separate N2recovery apparatus into the drier and the N2 apparatus can derive thenitrogen from the air. A separate microprocessor control may be providedfor controlling and monitoring the temperature profile, and anothermicroprocessor control for the oxygen concentration during the dryingoperation. Connections may be provided to the drier which supply thegaseous medium saturated with solvent and vapour to a cooling apparatusfor condensation, in particular at 3° C.

The plant or apparatus is also distinguished by operation of the drierunder approximately ambient pressure conditions.

Finally, the invention is also distinguished by the use of nitrogen froman apparatus recovering nitrogen from air and known per se in the drierof a cleaning machine for textiles operating free of FCHC.

The mode of operation of the drier is as follows: In the dryingoperation the gaseous medium in the closed drier is conducted via a fanpast a heat register (both within the drier) and heated to 55° C. Thehot air withdraws the solvent residual moisture from the textiles in arotating drum. The saturated hot air is cooled in a cooling apparatus to3° C., condensing out the solvent. The separated solvent is returned tothe cleaning machine. The solvent recovery is 99%. If required, thesolvent from two reservoirs of the cleaning machine is reprocessed inthe distillation unit.

In the drying, the solvent mentioned and consisting of pure hydrocarbonhaving a theoretical flashpoint of 71° C. is used, the drying beingcarried out 15° C. beneath the flashpoint.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of embodiment of the invention will now be explained indetail with the aid of the attached drawings, wherein:

FIG. 1 shows a schematic illustration of an apparatus which issurrounded by an outer wall to show how small the apparatus can beconstructed;

FIG. 2 shows such an apparatus from the constructional side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

On the left in FIG. 1 the cleaning machine 10 can be seen; supply drumsnot illustrated are provided beneath the cleaning machine. The cleaningmachine is drive via a motor gear-type unit 12.

At the start and during the entire drying operation, the oxygenconcentration within the drier is reduced to far beneath the theoreticalexplosion limit so that even when the flame point is exceeded noinflammable atmosphere can form in the drier. In contrast to the priorart, the nitrogen flushing in the drier takes place without any vacuum,being carried out on the contrary under approximately normal atmosphericpressure conditions.

In the same housing with the drive machine a filter 14 for the solventis provided. The illustration is schematic. In fact, two filters areinstalled above each other. The first of the two identically constructedfilters is the prefilter and the other the afterfilter.

A solvent cooler 13 is arranged laterally adjacent the filter 14 in thedrawings.

Finally, in the same housing magnetic valves 16 are also arranged forthe control functions of the cleaning machine.

Arranged alongside in the drawing is a distillation apparatus which isindirectly heated with steam via 20. 70 liters are withdrawn per hourfrom the distillation apparatus 24, cleaned, the bottom removed and thecondensate returned to the cleaning machine via 26.

Shown in the drawings completely on the right is an N2 apparatus whichis known per se and is not the subject of the invention; the effect (N2production) thereof is merely utilized. The N2 apparatus 30 receives airfrom the conduit 18. A filter and a pump are provided at 32. Theseoperate by a novel pressure alternating principle, the so-called"pressure swing absorption (PSA)": A pulsating pump effect is utilizedin an active carbon filter. Air is inspired and on ejection the filter32 repels oxygen. Via a conduit 36 the nitrogen passes to a reservoir 38from which via the conduit 40 nitrogen can be injected as desired intothe drier, in particular discontinuously, when the nitrogen content hasdropped below a predetermined limit or the oxygen content runs the riskof increasing above a predetermined limit (6%). An O2 measuring conduit44 leads from the control unit 42 to the drier 50.

The central part of the present invention is the drier 50 into whichnitrogen 40 is injected as protective gas. The clean material isintroduced into the drier for instance by a snorkel transfer method.Heating is effected by passage past a heating register (fan action) to55° C. in the closed system, i.e. 15° C. beneath the explosion point,thereby providing double safety because critical O2 values are neverreached. The residual moisture of the material being cleaned ispractically expelled by the heating to 55° C. The 55° C. hot medium issupplied to the refrigeration apparatus (not shown) where a cooling to3° C. is effected and the residual moisture condensed. After possiblecleaning the latter is returned to the cleaning machine. The drier isindirectly heated with vapour or steam 20. A rotating drum may beemployed.

The conditions in the drier are controlled via a microprocessor control.An O2 measuring device inspires fresh air. Prior to the drying operationa system is passed to the N2 apparatus. A flushing with N2 is carriedout until the oxygen content drops below 6%. Another signal indicatesreadiness for operation.

In FIG. 2, which shows a detail of the drier arrangement and N2preparation, the same reference numerals as in FIG. 1 have been used foridentical elements.

The drying drum 50 has been emphasized as the central element. Nitrogengenerated from the air is injected into the drum of the drier 50 via theconduit 40 past a heating register 60. The still moist material istransferred from the cleaning machine 10, not illustrated here.

The heating to the aforementioned temperature takes place in the drum50; the moisture and solvent are expelled (62). Recycling is effectedvia a fan 64. The mixture flows on at 66 and enters an evaporator 68,the liquid N2 being supplied together with condensed water via 70 to awater separator 72. The condensate is removed via 22. The steam returnsin the cycle at 20 to the heat register. Following the evaporator 68, ameasuring conduit 44 branches off to an O2 analyzer 74. An O2 value of6% is set in the drier.

The N2 apparatus 30 takes up air, compresses the latter at 78, filtersit at 32 and supplies it to adsorbers 80 and 81. The nitrogen generatedis supplied at 36 via an N2 reservoir 38, from which it is supplied viaa controlled flow meter 84 to the aforementioned N2 metering conduit. 62is a heating conduit.

The cleaning machine according to the invention thus does not cleaneither in vacuum or in gas-tight manner or under protective gas.

The invention has nothing in common with the prior art in which many PERmachines are simply modified for benzine or petrol (danger ofexplosion!).

According to the invention, the operation may be carried out with asolvent with high flashpoint of for example 71° C. at a low vapourpressure. This alone provides protection against explosion only in thedrying by means of hot air, i.e. rendering inert, this protection notbeing provided in the washing itself.

Due to the step according to the invention of separately washing anddrying (separate apparatus components, i.e. cleaning machine and drier),each aggregate can be designed to suit its optimum respective purpose.The transfer method, which is the foundation of the invention, thuspermits simultaneous washing and drying of different batches andtherefore gives twice the capacity (economical advantage for the user).The rendering inert takes place only in the drier and not in the washingdrum by the special aggregate which is employed specifically for thispurpose and which recovers nitrogen from the ambient air andconsequently dispenses with technically complicated vacuum method andgas-tight machines.

We claim:
 1. Method of dry cleaning of textiles comprising the stepsof:washing the textiles under atmospheric pressure in a separatecleaning machine using a solvent free of FCHC, free of aromates based onhydrocarbons having a flash point of at least 55° C. under low pressure;drying the textiles in a separate drier wherein the drying is conductedin a protection gas atmosphere having an oxygen content of at most 10%;condensing the solvent vapors, originating in the separate drier, to 3°C. creating thereby solvent condensate; and recycling the solventcondensate, for use in the cleaning machine.
 2. Method according toclaim 1, wherein said solvent free of FCHC is n-Unecane.
 3. Methodaccording to claim 1, wherein said protection gas is nitrogen.
 4. Methodaccording to claim 3, further comprising the step of generating, fromair taken from surrounding atmosphere, said nitrogen protection gas. 5.Method according to claim 1, further comprising the step of controllingtemperature in said drier during said drying to to at least 15° C. belowflash point of said solvent.
 6. Apparatus for cleaning textilematerials, comprising:a separate cleaning machine into which is placedthe textile material to be cleaned producing thereby cleaned textilematerial; a drier into which the cleaned textile materials are placedand into which protection gas is injected resulting in cleaned and driedtextile materials; a heating register for heating the protection gas;and a micro-processing control unit for controlling and regulatingtemperature and oxygen percentage within said drier.
 7. Apparatusaccording to claim 6, further comprising independent safety circuits forcontrol and monitoring of a temperature profile up to a limittemperature, in particular 55° C., approximately 15° C. beneath theflashpoint of the cleaning solvent, and for control and monitoring ofthe oxygen concentration in the drier when the drier is in operation, inparticular to 6%.
 8. Apparatus according to claim 6, wherein a fanwithin the drier conducts the gaseous drying medium to a heat register.9. Apparatus according to claim 6, further comprising connections at thedier for supplying the gaseous medium saturated with solvent and vaporsto a cooling apparatus for condensation of the solvent and vapors, inparticular at about 3° C.
 10. Apparatus according to claim 6, whereinthe drier operates approximately under ambient conditions.
 11. Apparatusaccording to claim 6, further comprising a distillation apparatus. 12.Apparatus according to claim 6, further comprising means for snorkeltransfer of the cleaned textile materials from the separate cleaningmachine into the separate drier.